In ancient China, a spit-out portion of rice revealed whether a
person was telling lies—dry rice indicated the dry mouth of a liar. Sound
unreliable? So is the polygraph test. Literally meaning "many writings," the word polygraph refers
to the simultaneous recordings of physiological reactions to various
emotional states.

Italian criminologist Cesare Lombroso, founder of the concept of
"the born criminal," was the first to utilize a lie detection test in
1895. And in 1921, John Larson invented the first polygraph. The version
used today, designed in the 1920s by Leonarde Keeler, records
respiration as well as sweat gland and cardiovascular activity.

Today, criminal and civil court cases can use polygraph tests to
narrow a list of suspects. Still, the findings are controversial because
different emotional responses elicit similar physiological responses. To
protect the innocent from being unjustly condemned, the American
Psychological Association declared in 1986 that the polygraph does not
yield definitive information. As a result, evidence from a lie detector
test is currently considered legally unacceptable in most
cases.